This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C xc2xa7119 from an application entitled Display Device Using Two Digital Display Panels earlier filed in the Korean Industrial Property Office on Nov. 6, 1999, and there duly assigned Serial No. 49103/1999 by that Office, and an application entitled Projection Display Device Using Two Liquid Crystal Display Panels earlier filed in the Korean Industrial Property Office on Nov. 2, 2000, and there duly assigned Serial No. 65045/2000 by that Office.
1. Field of the Invention
The present invention relates to a display device, and more particularly, to a display device using two liquid crystal display panels, by which the same maximum brightness as that of an existing display device adopting three liquid crystal display panels is obtained using only two liquid crystal display panels.
2. Description of the Related Art
Existing types of display devices that are driven in a digital system include plasma display panels (PDP), liquid crystal display (LCD) panels and ferroelectric liquid crystal (FLC) panels.
FLC panels have a structure in which ferroelectric liquid crystal is sandwitched between an optical planar mirror formed on a silicon substrate and glass, and have a wide viewing angle and a fast response speed compared to existing panels.
A exemplary display device using three LCD panels is made up of R, G and B controllers, an optical engine and a screen. The optical engine is made up of R, G and B LCD panels and an optical system which includes an optical source, a collimating lens, a polarized beam splitter, a reflective mirror and a projection lens.
The R, G and B controllers receive R, G and B signals, respectively, and control the offset, contrast and brightness of the received signals, perform signal processing such as gamma compensation, and generate R, G and B data on a field-by-field basis in synchronization with a vertical synchronization signal, respectively, to display the R, G and B data on the R, G and B LCD panels, respectively. Also, the R, G and B controllers each receive a vertical synchronization signal and a horizontal synchronization signal, and generate clock and panel control signals for controlling the R, G and B LCD panels, respectively.
In the optical engine, light emitted from the optical source is split into R, G and B light beams by the polarized light beam splitter, and the R, G and B light beams are projected to the R, G and B LCD panels, respectively, by the reflective mirror. Then, the R, G and B LCD panels transmit or reflect incident light beams corresponding to data values R, G and B applied by the R, G and B controllers to cells each formed as a matrix, under the control of the clock and panel control signal, and then display the light beams on the screen via the projection lens.
In a exemplary display device using three LCD panels, the use of three LCD panels increases the manufacturing costs and complicates the structure of an optical system. Also, the convergence of each of the R, G and B light must be adjusted, so that the number of process steps increases.
Incorporated by reference herein are U.S. Pat. No. 6,132,047 to Yoshitaka Itoh entitled Polarized Light Illumination Device which describes a three panel projector; U.S. Pat. No. 5,706,063 to Chang-wan Hong entitled Optical System Of A Reflection LCD which describes a two panel projector; U.S. Pat. No. 5,833,338 to Shlomo Barak entitled Projector which describes single panel and double panel projectors and the use of a color wheel for sequentially separating the R, G and B spectral components of a light beam from a light source; U.S. Pat. No. 5,784,038 to Dean Irwin entitled Color Projection System Employing Dual Monochrome Liquid Crystal Displays With Misalignment Correction which describes the use of two color wheels and two liquid crystal display panels in developing a projection image; and U.S. Pat. No.5,929,843 to Hiroshi Tanioka entitled Image Processing Apparatus Which Extracts White Component Data, where in the white component data is extracted from input R, G, B color data and generates Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data for displaying a full color image on a liquid crystal display panel.
Other references of interest to projection display devices are the following Japanese patents: JP11006980 to Mayashita Eimei entitled Projection Device; JP8168039 to Nomura Tomoyoshi et al. entitled Projection Display System And Projection Position Adjusting Method; JP9090402 to Takigawa Shinichi et al. entitled Picture Display Device; JP10123477 to Yoneda Toshiyuki et al. entitled Liquid Crystal Projector; JP10023445 to Semasa Takayoshi entitled Picture Display Device; JP8294138 to Ozuru Shosuke et al. entitled Liquid Crystal Projector; and JP10148885 to Endo Hiroaki et al. entitled Projector Apparatus
To solve the above problems, an objective of the present invention is to provide a display device adopting two liquid crystal display panels, by which the same maximum brightness as that in the case of adopting three liquid crystal display panels is obtained using only two liquid crystal display panels.
It is another object of the present invention to provide a low cost projection display device utilizing two liquid crystal display panels and a conversion algorithm for converting three-colors to four-colors such that a loss in color saturation is compensated for.
To achieve the above objective, the present invention provides a display device using two liquid crystal display panels, which is driven in a digital system, the device including: a controller for receiving first red, green and blue (R/G/B) data signals and generating, at intervals of one vertical period, a control signal for controlling the liquid crystal display panels and second red, green, blue Tom data signals and a white data signal, i.e., Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals, which are compensated for a loss in color saturation using a predetermined arithmetic algorithm; and an optical engine for outputting the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals to a screen via the two liquid crystal display panels according to the control signals.
Additionally, according to one aspect of the present invention, the optical engine utilizes a light source for emitting light; a collimating lens for collimating incident light from the light source into parallel light or focusing light; a color switching means responsive to a color switching control signal generated by the controller for sequentially separating red, green, blue and white light signals from light received from the collimating lens during one vertical period; a first beam splitter for passing P wave components of the red, green, blue and white light signals and orthogonally reflecting S wave components of the red, green, blue and white light signals; a first reflective mirror for reflecting the P wave components of the red, green, blue and white light signals to a first one of the liquid crystal display panels; a second reflective mirror for reflecting the S wave components of the red, green, blue and white light signals to a second one of the liquid crystal display panels; the first liquid crystal display panel receiving the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals and the P wave components of the red, green, blue and white light signals, and transmitting incident light corresponding to the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals; the second liquid crystal display panel receiving the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals and the S wave components of the red, green, blue and white light signals, and transmitting incident light corresponding to the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals; a second beam splitter for orthogonally reflecting S wave components of the incident light transmitted from the first liquid crystal display panel and passing P wave components of the incident light transmitted from the second liquid crystal display panel; and a lens for producing a magnified image from light output from the second beam splitter for display on the screen.
Also, according to another aspect of the present invention, the optical engine utilizes a light source for emitting light; a first beam splitter for passing a first wavelength of the light emitted from the light source and reflecting a second wavelength of the light emitted from the light source; a first collimating lens for collimating the first wavelength of light from the first beam splitter into parallel light or focusing light; a first reflective mirror for changing the direction of the second wavelength of light from the first beam splitter by reflecting the second wavelength of light; a second collimating lens for collimating the second wavelength of light from the first reflective mirror into parallel light or focusing light; first color switching means responsive to a color switching control signal generated by the controller for sequentially separating the light received from the first collimating lens into red, green, blue and white light signals during one vertical period; a second reflective mirror for changing the direction of the red, green, blue and white light signals from the first color switching means by reflecting the red, green, blue and white light signals from the first color switching means, the red, green, blue and white light signals reflected by the second reflective mirror being impinged upon a first one of the liquid crystal display panels; second color switching means responsive to the color switching control signal generated by the controller for sequentially separating the light received from the second collimating lens into red, green, blue and white light signals during the vertical period, the red, green, blue and white light signals generated by the second color switching means being impinged upon a second one of the liquid crystal display panels; the first liquid crystal display panel receiving the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals from the controller and the red, green, blue and white light signals generated by the first color switching means, and transmitting incident light corresponding to the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals; the second liquid crystal display panel receiving the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals from the controller and the red, green, blue and white light signals generated by the second color switching means, and transmitting incident light corresponding to the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals; a second beam splitter for orthogonally reflecting light transmitted from we the second liquid crystal display panel and passing light transmitted from the first liquid crystal display panel; and a lens for producing a magnified image from light output from the second beam splitter for display on the screen.
According to a further aspect of the present invention, the optical engine utilizes a light source for emitting light; a collimating lens for collimating incident light from the light source into parallel light or focusing light; a color switching means responsive to a color switching control signal generated by the controller for sequentially passing red, green, blue and white light signals during one vertical period; a beam splitter for passing P wave components of the red, green, blue and white light signals and orthogonally reflecting S wave components of the red, green, blue and white light signals; a first one of the liquid crystal display panels receiving the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals and the P wave components of the red, green, blue and white light signals, and reflecting incident light corresponding to the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals; a second one of the liquid crystal display panels receiving the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals and the S wave components of the red, green, blue and white light signals, and reflecting incident light corresponding to the Rxe2x80x2/Gxe2x80x2/Bxe2x80x2/W data signals; the beam splitter passing P wave components of the light reflected by the first liquid crystal display panel and orthogonally reflecting S wave components of the light reflected by the second liquid crystal display panel; and a lens for producing a magnified image from light output from the second beam splitter for display on the screen.